ORLANDO, FL USA (UroToday.com) - In this study, presented by Dr. Rashed Ghandour and colleagues from Columbia University, they investigated the independent impact of tumor volume and malignancy on renal function.
The study included 1 244 patients who had undergone radical or partial nephrectomy for a renal mass between 1990 and 2012. They retrospectively reviewed only those patients whose tumor was found to be renal cell carcinoma or benign (defined as oncocytoma and angiomyolipoma), excluding patients who were determined to have a malignancy other than renal cell carcinoma. Additionally, patients were excluded if the tumor was greater than 10 cm, was non-neoplastic, or a rare variant of histopathology.

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In addition to histopathological category, other measures included tumor size, estimated glomerular filtration rate (eGFR, using Modification of Diet in Renal Disease formula), and patient comorbidities. These variables were entered into a linear regression model to determine whether histopathology or volume were predictive of eGFR.

A total of 1 103 of the 1 244 patients included in the study had renal cell carcinoma; the remaining 141 had benign masses. In their linear regression model, malignant tumors were significantly associated with reduced eGFR (beta: -5.19, p=0.012). After including tumor size, in addition to several possible covariates in the model, the association slightly decreased but remained significant (beta: -3.90, p=0.03). Conversely, tumor volume was not independently predictive of eGFR (p=0.73).

From these data, they concluded that tumor histopathology, rather than tumor size, is independently predictive of renal function. Although statistically significant, it remains to be seen whether the reduction in GFR is clinically important. In the discussion following his presentation, Dr. Ghandour suggested that this finding is most relevant in providing additional context to understanding the impact of small renal masses and renal cell carcinoma on renal function. Given these findings, it may be interesting to prospectively evaluate renal function in a prospective cohort and perform similar analyses as those presented in this study, as well as an exploration of the effect of histopathological subtypes and pathologic grades. As more work is done in the area of active surveillance and in attempting to describe the ideal patient for expectant management versus intervention, knowing whether malignancy has a progressively deleterious effect on renal function and outcomes would be an intriguing next step.